1. Field of the Invention
The present invention relates to an image sensing system, and more specifically relates to an image sensing system wherein a plurality of electric signals responding to the quantity of incident light on a plurality of picture elements provided in photoelectric conversion elements array are once stored in storage parts and are sequentially outputted by a shift register.
2. Description of the Prior Art
An image sensing system is employed, for example, for automatic focus detecting device of a camera. Such image sensing system is used normally by integrating the quantity of charges responding to the quantity of incident light generated by a photoelectric conversion element array which responds to the light from a subject.
Then, in an image sensing system employed for such an automatic focus detecting device, a higher detecting speed of automatic focusing and a more improved system performance in the case with a subject of low luminance have been required. For that reason, efforts are being made to obtain a high sensitivity by expanding the area of photo-reception by larger photoelectric conversion elements or by improving the efficiency of conversion. However, such a measure causes the quantity of generated charges to saturate soon when an object is of high luminance, and therefore the integration time which is to be set in the system is required to be extremely short. Accordingly, a short-time integration controlling method has to be employed.
On the other hand, in the case of low luminance, charges generated by the photoelectric conversion elements array are integrated in the array itself and the charges are transferred to storage parts after completing the integration, but this takes a relatively long integration time, and therefore dark charges are generated in the storage parts in that time, and these charges are added to the charges transferred from the array, and therefore the output of the storage parts has an error.